Refinement of Ammonium Perrhenate Structure Using a Pseudo-Spin Model for the Ammonium Ion Orientation

Abstract

A new Rietveld refinement of previously reported powder neutron diffraction data on ND4ReO 4 taken over a wide range of temperatures [Powell, Brown, Harnden & Reid (1993). Acta Cryst. B49, 463-468] is reported. Rigid-body constraints are applied to the cation geometry and occupation of a second cation orientation at higher temperatures is permitted. The resulting structure at higher temperatures is to be preferred to the previous structure with a single cation orientation and supports the pseudo-spin theory of cooperative disordering without a phase transition.

Low-temperature behaviour of ammonium ion in buddingtonite [N(D/H)4AlSi3O8] from neutron powder diffraction

“…Similar orientational ordering is also exhibited by other minerals, for, e.g. ammonium perrhenate, (ND 4 ReO 4 ), (Swainson and Brown 1997). Powder neutron diffraction proved are effective means of studying such disordering processes and hence justifies our methodology.…”

Synthesis of highly destacked ReS2 layers embedded in amorphous carbon from a metal-organic precursor

“…5b). Diffractograms indicate that (Oct 4 N)ReO 4 crystallizes in a scheelitelike structure similar to that of the NH 4 ReO 4 reported by Swaison et al [27], but much more expanded, due to the large size of the tetraoctylammonium cation. All diffraction peaks (Fig.…”

Ammonium cyanate: a DFT study of crystal structure, rotational barriers and vibrational spectrum

“…The cation site symmetry and the arrangement of the nearest atoms in ammonium cyanate are similar to those in the ammonium scheelites [9]. Initially, it was thought that if the energy difference between the two orientations of the ammonium cation were not too large, pseudo-spin effects may affect the thermal expansion and other physical properties of ammonium cyanate, in the same manner as in ammonium perrhenate and ammonium metaperiodate.…”